/***************************************************************************

    TITLE:		atmos_62

----------------------------------------------------------------------------

    FUNCTION:		1962 atmosphere table interpolation routine

----------------------------------------------------------------------------

    MODULE STATUS:	developmental

----------------------------------------------------------------------------

    GENEALOGY:	Created 920827 by Bruce Jackson as part of the C-castle
		development effort.

----------------------------------------------------------------------------

    DESIGNED BY:	B. Jackson

    CODED BY:		B. Jackson

    MAINTAINED BY:	B. Jackson

----------------------------------------------------------------------------

    MODIFICATION HISTORY:

	DATE	PURPOSE							BY
	931220	Added ambient pressure and temperature as outputs.	EBJ
	940111	Changed includes from "ls_eom.h" to "ls_types.h" and
		"ls_constants.h"; changed DATA to SCALAR types.		EBJ

----------------------------------------------------------------------------

    REFERENCES:

    [ 1]	Hornbeck, Robert W.: "Numerical Methods", Prentice-Hall,
		1975.  ISBN  0-13-626614-2

----------------------------------------------------------------------------

    CALLED BY:

----------------------------------------------------------------------------

    CALLS TO:

----------------------------------------------------------------------------

    INPUTS:

----------------------------------------------------------------------------

    OUTPUTS:

--------------------------------------------------------------------------*/

#include "ls_types.h"
#include "ls_constants.h"

#include "atmos_62.h"

#include <math.h>

#define	alt_0	d_a_table[index  ][0]
#define	alt_1	d_a_table[index+1][0]
#define	den_0	d_a_table[index  ][1]
#define den_1	d_a_table[index+1][1]
#define	sps_0	d_a_table[index  ][2]
#define	sps_1	d_a_table[index+1][2]
#define gden_0	d_a_table[index  ][3]
#define	gden_1	d_a_table[index+1][3]
#define	gsps_0	d_a_table[index  ][4]
#define gsps_1	d_a_table[index+1][4]

#define MAX_ALT_INDEX 121
#define DELT_ALT 2000.
#define HLEV 36089.
#define TAMB0 518.7
#define PAMB0 2113.8
#define MAX_ALTITUDE 240000.

void ls_atmos( SCALAR altitude, SCALAR * sigma, SCALAR * v_sound, 
		SCALAR * t_amb, SCALAR * p_amb )
{

    int		index;
    SCALAR	daltp, daltn, daltp3, daltn3, density;
    SCALAR	t_amb_r, p_amb_r;
    SCALAR      tmp;

    static SCALAR	d_a_table[MAX_ALT_INDEX][5] =
    {
	{      0.,	 2.37701E-03,	 1.11642E+03,	 0.00000E+00,	 0.00000E+00	},
	{   2000.,	 2.24098E-03,	 1.10872E+03,	 1.92857E-12,	-1.75815E-08	},
	{   4000.,	 2.11099E-03,	 1.10097E+03,	 1.34570E-12,	-1.21740E-08	},
	{   6000.,	 1.98684E-03,	 1.09315E+03,	 1.44862E-12,	-1.47225E-08	},
	{   8000.,	 1.86836E-03,	 1.08529E+03,	 1.36481E-12,	-1.44359E-08	},
	{  10000.,	 1.75537E-03,	 1.07736E+03,	 1.32716E-12,	-1.45340E-08	},
	{  12000.,	 1.64768E-03,	 1.06938E+03,	 1.27657E-12,	-1.44280E-08	},
	{  14000.,	 1.54511E-03,	 1.06133E+03,	 1.24656E-12,	-1.62540E-08	},
	{  16000.,	 1.44751E-03,	 1.05323E+03,	 1.19220E-12,	-1.50560E-08	},
	{  18000.,	 1.35469E-03,	 1.04506E+03,	 1.15463E-12,	-1.65220E-08	},
	{  20000.,	 1.26649E-03,	 1.03683E+03,	 1.11926E-12,	-1.63562E-08	},
	{  22000.,	 1.18276E-03,	 1.02853E+03,	 1.07333E-12,	-1.70533E-08	},
	{  24000.,	 1.10333E-03,	 1.02016E+03,	 1.03743E-12,	-1.59305E-08	},
	{  26000.,	 1.02805E-03,	 1.01173E+03,	 1.00195E-12,	-2.27248E-08	},
	{  28000.,	 9.56760E-04,	 1.00322E+03,	 9.39764E-13,	 3.29851E-10	},
	{  30000.,	 8.89320E-04,	 9.94641E+02,	 1.01399E-12,	-8.80946E-08	},
	{  32000.,	 8.25570E-04,	 9.85988E+02,	 5.39268E-13,	 2.41048E-07	},
	{  34000.,	 7.65380E-04,	 9.77258E+02,	 2.16894E-12,	-9.91599E-07	},
	{  36000.,	 7.08600E-04,	 9.68448E+02,	-4.10001E-12,	 3.60535E-06	},
	{  38000.,	 6.44190E-04,	 9.68053E+02,	 2.78612E-12,	-8.07290E-07	},
	{  40000.,	 5.85146E-04,	 9.68053E+02,	 1.00455E-12,	 2.16313E-07	},
	{  42000.,	 5.31517E-04,	 9.68053E+02,	 1.31819E-12,	-5.79609E-08	},
	{  44000.,	 4.82801E-04,	 9.68053E+02,	 1.09217E-12,	 1.55309E-08	},
	{  46000.,	 4.38554E-04,	 9.68053E+02,	 1.01661E-12,	-4.16262E-09	},
	{  48000.,	 3.98359E-04,	 9.68053E+02,	 9.19375E-13,	 1.11961E-09	},
	{  50000.,	 3.61850E-04,	 9.68053E+02,	 8.34886E-13,	-3.15801E-10	},
	{  52000.,	 3.28686E-04,	 9.68053E+02,	 7.58579E-13,	 1.43600E-10	},
	{  54000.,	 2.98561E-04,	 9.68053E+02,	 6.89297E-13,	-2.58597E-10	},
	{  56000.,	 2.71197E-04,	 9.68053E+02,	 6.25735E-13,	 8.90788E-10	},
	{  58000.,	 2.46341E-04,	 9.68053E+02,	 5.69765E-13,	-3.30456E-09	},
	{  60000.,	 2.23765E-04,	 9.68053E+02,	 5.15206E-13,	 1.23274E-08	},
	{  62000.,	 2.03256E-04,	 9.68053E+02,	 4.69912E-13,	-4.60052E-08	},
	{  64000.,	 1.84627E-04,	 9.68053E+02,	 4.25146E-13,	 1.71693E-07	},
	{  66000.,	 1.67616E-04,	 9.68314E+02,	 2.56502E-13,	-2.49268E-07	},
	{  68000.,	 1.51855E-04,	 9.68676E+02,	 4.23844E-13,	 9.76878E-07	},
	{  70000.,	 1.37615E-04,	 9.71034E+02,	 3.29621E-13,	-6.64245E-07	},
	{  72000.,	 1.24744E-04,	 9.72390E+02,	 3.11170E-13,	 1.77102E-07	},
	{  74000.,	 1.13107E-04,	 9.73745E+02,	 2.76697E-13,	-4.56627E-08	},
	{  76000.,	 1.02584E-04,	 9.75099E+02,	 2.53043E-13,	 4.04902E-09	},
	{  78000.,	 9.30660E-05,	 9.76450E+02,	 2.18633E-13,	 2.49667E-08	},
	{  80000.,	 8.44530E-05,	 9.77799E+02,	 2.29927E-13,	-1.06916E-07	},
	{  82000.,	 7.67140E-05,	 9.78950E+02,	 1.72660E-13,	 1.05696E-07	},
	{  84000.,	 6.97010E-05,	 9.80290E+02,	 1.68432E-13,	-3.23682E-08	},
	{  86000.,	 6.33490E-05,	 9.81620E+02,	 1.45113E-13,	 8.77690E-09	},
	{  88000.,	 5.75880E-05,	 9.82950E+02,	 1.37617E-13,	-2.73938E-09	},
	{  90000.,	 5.23700E-05,	 9.84280E+02,	 1.18918E-13,	 2.18061E-09	},
	{  92000.,	 4.76350E-05,	 9.85610E+02,	 1.11210E-13,	-5.98306E-09	},
	{  94000.,	 4.33410E-05,	 9.86930E+02,	 9.77408E-14,	 6.75162E-09	},
	{  96000.,	 3.94430E-05,	 9.88260E+02,	 9.18264E-14,	-6.02343E-09	},
	{  98000.,	 3.59080E-05,	 9.89580E+02,	 7.94534E-14,	 2.34210E-09	},
	{ 100000.,	 3.26960E-05,	 9.90900E+02,	 7.48600E-14,	-3.34498E-09	},
	{ 102000.,	 2.97810E-05,	 9.92210E+02,	 6.66067E-14,	-3.96219E-09	},
	{ 104000.,	 2.71320E-05,	 9.93530E+02,	 5.77131E-14,	 3.41937E-08	},
	{ 106000.,	 2.46980E-05,	 9.95410E+02,	 2.50410E-14,	 7.07187E-07	},
	{ 108000.,	 2.24140E-05,	 9.99070E+02,	 6.71229E-14,	-1.92943E-07	},
	{ 110000.,	 2.03570E-05,	 1.00272E+03,	 4.69675E-14,	 4.95832E-08	},
	{ 112000.,	 1.85010E-05,	 1.00636E+03,	 4.65069E-14,	-2.03903E-08	},
	{ 114000.,	 1.68270E-05,	 1.00998E+03,	 4.00047E-14,	 1.97789E-09	},
	{ 116000.,	 1.53150E-05,	 1.01359E+03,	 3.64744E-14,	-2.52130E-09	},
	{ 118000.,	 1.39480E-05,	 1.01719E+03,	 3.15976E-14,	-6.89271E-09	},
	{ 120000.,	 1.27100E-05,	 1.02077E+03,	 3.06351E-14,	 9.21465E-11	},
	{ 122000.,	 1.15920E-05,	 1.02434E+03,	 2.58618E-14,	-8.47587E-09	},
	{ 124000.,	 1.05790E-05,	 1.02789E+03,	 2.34176E-14,	 3.81135E-09	},
	{ 126000.,	 9.66010E-06,	 1.03144E+03,	 2.16178E-14,	-6.76951E-09	},
	{ 128000.,	 8.82710E-06,	 1.03497E+03,	 1.89611E-14,	-6.73330E-09	},
	{ 130000.,	 8.07070E-06,	 1.03848E+03,	 1.74377E-14,	 3.70270E-09	},
	{ 132000.,	 7.38380E-06,	 1.04199E+03,	 1.55382E-14,	-8.07752E-09	},
	{ 134000.,	 6.75940E-06,	 1.04548E+03,	 1.41595E-14,	-1.39263E-09	},
	{ 136000.,	 6.19160E-06,	 1.04896E+03,	 1.27239E-14,	-1.35196E-09	},
	{ 138000.,	 5.67490E-06,	 1.05243E+03,	 1.15951E-14,	-8.19953E-09	},
	{ 140000.,	 5.20450E-06,	 1.05588E+03,	 1.03459E-14,	 4.15010E-09	},
	{ 142000.,	 4.77570E-06,	 1.05933E+03,	 9.42149E-15,	-8.40086E-09	},
	{ 144000.,	 4.38470E-06,	 1.06276E+03,	 8.66820E-15,	-5.46671E-10	},
	{ 146000.,	 4.02820E-06,	 1.06618E+03,	 7.65573E-15,	-4.41246E-09	},
	{ 148000.,	 3.70260E-06,	 1.06959E+03,	 7.05890E-15,	 3.19650E-09	},
	{ 150000.,	 3.40520E-06,	 1.07299E+03,	 6.40867E-15,	-2.33736E-08	},
	{ 152000.,	 3.13330E-06,	 1.07637E+03,	 5.55641E-15,	 6.02977E-08	},
	{ 154000.,	 2.88480E-06,	 1.07975E+03,	 6.46568E-15,	-2.17817E-07	},
	{ 156000.,	 2.66270E-06,	 1.08202E+03,	 8.18087E-15,	-8.54029E-07	},
	{ 158000.,	 2.46830E-06,	 1.08202E+03,	 2.36086E-15,	 2.28931E-07	},
	{ 160000.,	 2.28810E-06,	 1.08202E+03,	 3.67571E-15,	-6.16972E-08	},
	{ 162000.,	 2.12120E-06,	 1.08202E+03,	 2.88632E-15,	 1.78573E-08	},
	{ 164000.,	 1.96640E-06,	 1.08202E+03,	 2.92903E-15,	-9.73206E-09	},
	{ 166000.,	 1.82300E-06,	 1.08202E+03,	 2.49757E-15,	 2.10709E-08	},
	{ 168000.,	 1.69000E-06,	 1.08202E+03,	 2.68069E-15,	-7.45517E-08	},
	{ 170000.,	 1.56680E-06,	 1.08202E+03,	 1.47966E-15,	 2.77136E-07	},
	{ 172000.,	 1.45250E-06,	 1.08202E+03,	 4.75068E-15,	-1.03399E-06	},
	{ 174000.,	 1.35240E-06,	 1.07963E+03,	 8.17622E-16,	 2.73830E-07	},
	{ 176000.,	 1.25880E-06,	 1.07723E+03,	 1.72883E-15,	-7.63301E-08	},
	{ 178000.,	 1.17130E-06,	 1.07482E+03,	 1.41704E-15,	 1.64901E-08	},
	{ 180000.,	 1.08960E-06,	 1.07240E+03,	 1.30299E-15,	-4.63038E-09	},
	{ 182000.,	 1.01320E-06,	 1.06998E+03,	 1.32100E-15,	 2.03140E-09	},
	{ 184000.,	 9.41950E-07,	 1.06756E+03,	 1.13799E-15,	-3.49522E-09	},
	{ 186000.,	 8.75370E-07,	 1.06513E+03,	 1.13202E-15,	-3.05052E-09	},
	{ 188000.,	 8.13260E-07,	 1.06269E+03,	 1.03892E-15,	 6.97283E-10	},
	{ 190000.,	 7.55320E-07,	 1.06025E+03,	 9.67290E-16,	 2.61383E-10	},
	{ 192000.,	 7.01260E-07,	 1.05781E+03,	 9.11920E-16,	-1.74281E-09	},
	{ 194000.,	 6.50850E-07,	 1.05536E+03,	 8.60032E-16,	-8.29013E-09	},
	{ 196000.,	 6.03870E-07,	 1.05290E+03,	 7.92951E-16,	 1.99033E-08	},
	{ 198000.,	 5.60110E-07,	 1.05044E+03,	 7.98164E-16,	-7.13232E-08	},
	{ 200000.,	 5.19320E-07,	 1.04798E+03,	 4.69394E-16,	 2.65389E-07	},
	{ 202000.,	 4.81340E-07,	 1.04550E+03,	 1.53926E-15,	-1.02023E-06	},
	{ 204000.,	 4.47960E-07,	 1.04063E+03,	 2.73571E-16,	 2.30547E-07	},
	{ 206000.,	 4.16690E-07,	 1.03565E+03,	 5.31456E-16,	-6.69551E-08	},
	{ 208000.,	 3.87320E-07,	 1.03065E+03,	 4.50605E-16,	 7.27308E-09	},
	{ 210000.,	 3.59790E-07,	 1.02562E+03,	 4.26126E-16,	-7.13720E-09	},
	{ 212000.,	 3.33970E-07,	 1.02057E+03,	 4.09893E-16,	-8.72426E-09	},
	{ 214000.,	 3.09780E-07,	 1.01549E+03,	 3.79301E-16,	-2.96576E-09	},
	{ 216000.,	 2.87120E-07,	 1.01039E+03,	 3.67902E-16,	-9.41272E-09	},
	{ 218000.,	 2.65920E-07,	 1.00526E+03,	 3.39092E-16,	-4.38337E-09	},
	{ 220000.,	 2.46090E-07,	 1.00011E+03,	 3.30732E-16,	-3.05378E-09	},
	{ 222000.,	 2.27570E-07,	 9.94940E+02,	 3.02981E-16,	-1.34015E-08	},
	{ 224000.,	 2.10270E-07,	 9.89730E+02,	 2.87343E-16,	-3.34027E-09	},
	{ 226000.,	 1.94120E-07,	 9.84500E+02,	 2.72646E-16,	-3.23743E-09	},
	{ 228000.,	 1.79060E-07,	 9.79250E+02,	 2.57074E-16,	-1.37100E-08	},
	{ 230000.,	 1.65030E-07,	 9.73960E+02,	 2.44060E-16,	-1.92258E-09	},
	{ 232000.,	 1.51970E-07,	 9.68650E+02,	 2.21687E-16,	-8.59969E-09	},
	{ 234000.,	 1.39810E-07,	 9.63310E+02,	 2.19191E-16,	-8.67865E-09	},
	{ 236000.,	 1.28510E-07,	 9.57940E+02,	 1.91549E-16,	-1.68569E-09	},
	{ 238000.,	 1.18020E-07,	 9.52550E+02,	 2.29613E-16,	-1.45786E-08	},
	{ 240000.,	 1.08270E-07,	 9.47120E+02,	 0.00000E+00,	 0.00000E+00	}
    };

    /* for purposes of doing the table lookup, force the incoming
       altitude to be >= 0 */

    // printf("altitude = %.2f\n", altitude);

    if ( altitude < 0.0 ) {
	altitude = 0.0;
    }

    // printf("altitude = %.2f\n", altitude);

    index = (int)( altitude / 2000 );
    if (index > (MAX_ALT_INDEX-2))
    {
     index = MAX_ALT_INDEX-2; /* limit maximum altitude */
     altitude = MAX_ALTITUDE;
    }
    if (index < 0) index = 0;
    daltp = alt_1 - altitude;
    daltp3 = daltp*daltp*daltp;
    daltn = altitude - alt_0;
    daltn3 = daltn*daltn*daltn;
    
    density = (gden_0/6)*((daltp3/2000) - 2000*daltp)
			    + (gden_1/6)*((daltn3/2000) - 2000*daltn)
			    + den_0*daltp/2000 + den_1*daltn/2000;
			    
    *v_sound = (gsps_0/6)*((daltp3/2000) - 2000*daltp)
			    + (gsps_1/6)*((daltn3/2000) - 2000*daltn)
			    + sps_0*daltp/2000 + sps_1*daltn/2000;

    *sigma = density/SEA_LEVEL_DENSITY;

    if (altitude < HLEV)    /* BUG - these curve fits are only good to about 75000 ft */
      {
	t_amb_r = 1. - 6.875e-6*altitude;
	// printf("index = %d  t_amb_r = %.2f\n", index, t_amb_r);
	// p_amb_r = pow( t_amb_r, 5.256 );
	tmp = 5.256; // avoid a segfault (?)
	p_amb_r = pow( t_amb_r, tmp );
	// printf("p_amb_r = %.2f\n", p_amb_r);
      }
    else
      {
	t_amb_r = 0.751895;
	p_amb_r = 0.2234*exp( -4.806e-5 * (altitude - HLEV));
      }

    *p_amb = p_amb_r * PAMB0;
    *t_amb = t_amb_r * TAMB0;

/* end of atmos_62 */
}
/**************************************************************************/
